void main(List<String> args) {
  Map map = {"name": "张三", "age": 18, "sex": "男"};
  print(map);
  // ps: Dart中的map不存在get方法;而是使用[]进行获取;
  print(map["name"]);
  print(map["age"]);
  print(map["sex"]);
  print(map.length);
  print(map.isEmpty);
  print(map.isNotEmpty);
  print(map.keys);
  print(map.values);
  print(map.containsKey("name"));
  map.forEach((key, value) => print("key:${key},value:${value}"));
  map.clear();
  print("清空后");
  map.forEach((key, value) => print("key:${key},value:${value}"));
}
